Attentional Dynamics Explain the Elusive Nature of Context Effects

Context effects in multi-alternative, multi-attribute choice are pervasive and yet, paradoxically, elusive at the same time. For example, simple changes to the spatial layout of alternatives on the screen can nullify or reverse the effects. Despite the success of dynamic decision models in explaining the occurrence of context effects, a coherent theory for understanding their elusiveness is currently lacking. We introduce a novel theoretical framework that relies on attention modulated comparisons to explain the elusive nature of context effects. We show via simulation that our model produces the attraction, compromise, and similarity effects simply by assuming that more time is spent comparing alternatives that are more similar. However, when more time is spent comparing dissimilar alternatives, model simulations reveal a reversal of the attraction and compromise effects. The empirical support for this model-based prediction is assessed by manipulating similarity-based attention in separate experiments for the three context effects (total N = 317). Further, by allowing the spatial organization of information to constrain the attention process, the model can explain changes in context effects induced by display layout. We show that the model's spatial attention mechanism allows it to capture presentation order effects in a reanalysis of previously published data. Finally, we develop a continuous approximation of the full model that permits fitting of choices and response times. In summary, the proposed framework provides a new tool for understanding not only the existence of context effects in choice, but also the attentional factors that lead to null or reversed context effects.